Associative Learning

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Associative Learning
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Challenge Questions

• You are a psychologist treating a patient who is
  addicted to smoking. Explain how you would treat
  the patients addiction.
• You are a therapist who has a patient with a fear
  of spiders. Their spouse loves the outdoors and
  this fear interfering with their marriage. How
  would you treat this patient?
• You are a coach of a football team and your
  quarterback is throwing too many incomplete
  passes. Explain how you would use learning theory
  to help his game.

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The Smokers Brain

• The smoker would care.
• Nicotine influences the levels of certain
  neurotransmitters.
• Nicotine can prevent the break down of dopamine,
  increasing its presence in brain neurons.
• This causes the pleasurable effects of smoking.

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The Phobics Brain

• The amygdala is activated by a relatively
  harmless stimulus.
• This creates a fear response.
• In a patient with a phobia inhibition by the
  prefrontal cortex does not occur.

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The Quarterbacks Brain

• The cerebellum coordinates and controls movement.
• Despite its small volume, it contains nearly half
  the cells in the entire brain.
• Cerebellar damage impairs the timing of ones
  movements.

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Outside of the Black Box

• Learning is something that can be observed
  without observing the brain directly.
• In fact, behavioral psychologists treat the
  nervous system as a black box and focus mainly
  on relationships among observable stimuli and
  behaviors.

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ASSOCIATIVE LEARNING
There are two types of associative learning

• Classical conditioning learning associations
  between objects.
• learning associations between objects.
• Operant conditioning learning that, in a
  particular situation, a certain response leads to
  a certain outcome.

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Classical Conditioning
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Ivan Pavlov

• Classical Conditioning was discovered by the work
  of Ivan Pavlov.
• He was studying digestive physiology for which he
  won the Noble Prize.

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CLASSICAL CONDITIONING

• An object or an event that you sense is referred
• to as a stimulus
• We distinguish two types of stimuli and responses

• Unconditioned stimulus (US)
  A stimulus that naturally
  evokes a response or reflex called the
  Unconditioned Response (UR)

• Conditioned stimulus (CS) A stimulus that does
  not naturally evoke a response. However, it can
  acquire the ability to elicit the response,
  called the Conditioned Response (CR).

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PAVLOVS EXPERIMENT
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Stimulus Generalization

• Stimulus Generalization occurs when animals
  respond more to stimuli that are similar to the
  original than to those which are different.
• Example The dog in Pavlovs experiment would
  also salivate to tones of similar frequencies to
  the original.

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Stimulus Generalization Gone Wrong!

• In 1920, little Albert, an eleventh month old
  orphan, learned to fear a rabbit.
• Eventually all white fuzzy objects caused the
  same fear in little Albert even though they were
  not paired with the US (loud sound).

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Stimulus Discrimination

• Stimulus Discrimination occurs when animals are
  conditioned to respond to one specific CS and not
  others.
• Example Only a tone of a specific frequency is
  followed by food. Other tone frequencies are
  presented without food. As a result, the dog only
  salivates after the tone of a specific frequency.

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The Sequence of Events

• Acquisition the gradual increase in the strength
  of a response that occurs with the pairing of a
  CS with a US.
• Extinction occurs when the CS is presented
  without the US causing a decrease in the strength
  of the response.

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Classical or Pavlovian Conditioning
Graph from Myers 6th Ed.
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Operant Conditioning
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OPERANT CONDITIONING

• The frequency of a behavior is influenced by the
  presence or absence of a rewarding or aversive
  event after the expression of this behavior
• This theory is called Behaviorism

B.F. Skinner developed the Skinner box to study
this type of learning in pigeons. The pigeons
learned to press levers to receive a reward!
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Sequence of Events

• Acquisition The animals response produces a
  reinforcer.
• Example A rat presses a bar that produces food.
  The rat will begin to press the bar more
  frequently.
• Extinction The animals response no longer
  produces a reinforcer.
• Example A rat presses a bar but it no longer
  produces food. The rat will press the bar less
  frequently.

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Schedules of Reinforcement
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Examples of Schedules
Variable Ratio Schedule A rat is given food for
pressing a lever an average of 3 times.
Fixed Ratio Schedule A rat is given food for
pressing a lever every 3 times.
Fixed Interval Schedule A rat is given food for
pressing a lever after 1 minute has elapsed.
Variable Interval Schedule A rat is given food
for pressing a lever after an average of
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Associative LearningADAPTIVE TIMINGADVANCED
MODELINGCLASSROOM PRESENTATION
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WHAT NEEDS TO BE MODELED?
Anatomy
Neurophysiology
A Complete Circuit!
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EXPERIMENTAL PROTOCOL

• US air puff

CS sound
UR, CR nictitating membrane extension
Learning phase for a selected number of trials,
the sound is presented before the air puff (in
delay or trace conditioning) Testing phase
the sound alone is presented to test for CR
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TIMING IS EVERYTHING!

• The eye blink is a very transient response must
  be made just prior to the air puff.
• If it is done too late, the eye is not protected
  when the air puff occurs.
• If it is done too early, the eye is not protected
  either since the blink ends too early!

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EXPLAINING ADAPTIVE TIMING

• How does the brain learn to execute the right
  response at the right time?
• We need to consider the neural circuits involved
  in producing the eye blink response
• The critical structure is the cerebellum

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THE BIG ISSUES

• The brain must have a way to keep track of time.
  It must have some kind of internal clock
• Learning may take place over many trials
  learning occurs at a certain rate which can vary
• Both aspects can be studied through mathematical
  models

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INTERNAL CLOCK IN THE CEREBELLUM

• Through a complex chemical process, some cells in
  the cerebellum can represent how much time has
  elapsed since a conditioned stimulus (CS) was
  presented
• The same cells can also learn to associate the
  unconditioned stimulus (US) with the CS
• Thus, these cells learn to time conditioned
  responses (CR)

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ANATOMY OF A NEURON
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CEREBELLAR CIRCUIT

• The circuitry involved in adaptive timing
  involves a several types of cells connected in
  very specific circuits
• The diagram illustrates that different circuits
  or pathways support specific sensory input (US,
  CS) and motor output (CR)

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US PATHWAY
The US signal due to the air puff to the eye
travels in the pathway outlined in red First it
is relayed to the inferior olivary cell Then it
is communicated the Purkinje cell through
climbing fibers
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CS PATHWAY
The CS signal due to the tone travels in the
pathway outlined in green First it is relayed to
the pontine nuclei Then it is sent to granule
cells through mossy fibers Finally, it reaches
Purkinje cells via parallel fibers
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CR PATHWAY
Purkinje cells influence cells in the
interpositus nuclei, which directly control the
expression of the CR through a series of
projections ending at the facial nucleus The
facial nucleus emits the appropriate motor
response to cause the blink
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The Central Circuitry Involved in Adaptive Timing
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Required Parameters for the Cerebellar Model of
Adaptive Timing of Eye Blinks
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING
INQUIRY THROUGH SOFTWARE 1
Model 1 Simple user interface for virtual
experiments (for less experienced students)
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING
INQUIRY THROUGH SOFTWARE 1
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING
INQUIRY THROUGH SOFTWARE 2
Model 2 More complex interface for more
experienced users
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING
INQUIRY THROUGH SOFTWARE 3
Model 3 Most functionality for most experienced
users